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Faecal pharmacy Termites cause $40 billion in damage every year, worldwide, and researchers say the insects have developed an ingenious defence against pesticide: They make antibacterial nests out of their own poo.

Termites have evolved to use their faeces as a source of natural antibiotics, according to a report in the latest Proceedings of the Royal Society B . By integrating their poo into building materials, termite nests prevent the spread of disease and counter certain insecticides.

An average termite is only a centimetre long, yet these tiny subterranean insects have foiled humans for centuries.

"With the Formosan subterranean termites, the nest can be spread in the ground over 150 metres through a complex system of tunnels," says Chouvenc, a researcher at the University of Florida. "They are therefore difficult to detect, and usually people notice them in their house after extensive damage becomes visible."

There are about 3000 described species of termites, but only 80 are considered as structural pests. The Formosan termite is now under countless homes in subtropical and temperate areas, he says. The Eastern subterranean termite, native to the United States, is also prevalent.

Chouvenc and his team collected five Formosan termite colonies. The researchers analysed the nests, including performing tests to determine the antimicrobial activity.

The scientists determined that the poo-containing nest material promoted the growth of Streptomyces, a beneficial bacteria. It, in turn, prevented infection caused by other microbes.

Three-pronged defence

This mode of defence adds to the termites' already powerful disease-resistant arsenal. It's a three-part punch that helps them win battles with homeowners.

First, termites possess an innate immunity, due to their biochemistry, which wards off bodily intruders, such as bacteria and pesticides.

"Second," Chouvenc says, "termites have what is now accepted as 'social immunity,' as they can increase their disease resistance as a group with the help of prophylactic behaviours (such as grooming, cadaver removal and cannibalism)."

This third, most recently discovered defence, likely evolved because "subterranean termites have survived in the soil in constant contact with a variety of pathogens." They also produce a lot of poo that accumulates in their confined environment. It's a win-win for them to recycle the faeces into a building material.

Humans aren't so lucky, in terms of this form of recycling. Due to the termites' diet, their faecal material consists mostly of partially digested wood, a resource that is poor in nitrogen and therefore limits the growth of many organisms.

"The big difference here is that, while we have beneficial bacteria inside ourselves, termites were able to partially export it outside to maintain a clean environment," Chouvenc says.

Rebeca Rosengaus also studies termites and is an associate professor in the Department of Marine and Environmental Sciences at Northeastern University.

She says that "a variety of insects -- both solitary and social -- exploit the chemicals of Streptomyces to control parasites and/or pathogens."

Based on the latest study, which she says is "well thought out and well presented," Rosengaus agrees that termites should be added to the list of insects with antibiotic powers.